1. Field of the Invention
The present invention relates to a nitride based semiconductor laser device having a nitride based semiconductor layer.
2. Description of the Background Art
In recent years, nitride-based semiconductor laser devices have been utilized as light sources for next-generation large-capacity disks and have been actively developed.
In such nitride-based semiconductor laser devices, the plane directions of main surfaces of active layers are taken as substantial (H, K, —H—K, O) planes such as (11 20) planes or (1 100) planes, so that piezoelectric fields generated in the active layers can be reduced. As a result, it is known that the luminous efficiency of laser light can be improved. Here, H and K, described above, are any integers, and at least one of H and K is an integer other than zero.
Furthermore, it has been known that the gains of the nitride based semiconductor laser devices can be improved by setting the (0001) planes and the (000 1) planes to pairs of cavity facets (see, for example, JP 8-213692A and Japanese Journal of Applied Physics Vol. 46, No. 9, 2007, pp. L187˜L189).
In the above-mentioned nitride based semiconductor laser devices, however, protective films formed on the cavity facets are easily stripped.